6. The Soviet atomic bomb
At the end of the Second World War, the United States possessed the largest Navy in the world, the largest Air Force, and a weapon used only twice thus far in history, the atomic bomb. America’s exclusive ownership of atomic bombs lasted less than five years. In 1949 the Soviet Union, aided by Americans sympathetic to communism who conducted espionage on their behalf, successfully detonated an atomic bomb. The 1950s brought in a new belief at the end of the world, as the Soviets and the United States developed more powerful atomic bombs. By the middle of the decade and even more powerful weapon, the thermonuclear bomb, appeared in the arsenals of both.
At the same time, throughout the years of the Eisenhower Administration, relations between the Soviet Union and the United States deteriorated into the Cold War. Fear of nuclear annihilation grew throughout the decade of the 1950s. Both the USSR and the United States developed new means of delivering nuclear weapons, from submarines and from land-based ballistic missiles. Both nations experimented with atomic cannon, portable atomic weapons (such as the Davy Crockett, the smallest nuclear system ever deployed), and other tactical uses of the nuclear bomb. The widespread belief the next major war would end humanity on earth developed steadily through the 1950s and 1960s.